Answer:
C
Explanation:
Many kinds of air pollution can't be seen, which means A is incorrect. Any kind of pollution can be harmful to you, which means B is incorrect too. Air pollution is very harmful but in most cases can't be directly seen, so C is correct. Pollution can be found everywhere, so D is incorrect also.
Tissues
Tissues are somewhat more complex units than cells. By definition, a tissue is an organization of a great many similar cells with varying amounts and kinds of nonliving, intercellular substance between them.
Gene mutations can be passed on to future generations and drive natural selection. ... Gene mutations can be helpful, harmful, or neutral for an organism's survival. Only mutations that are helpful in the organism's environment would influence its survival and reproduction